Have you ever purchased a product from e-commerce site? Many chances are that you would have received recommendations when you loged into the site next time or through mailers about products that are similar to what you have purchased before.
If you buy a DSLR camera , the site will recommend DLSR from other brands.
If you buy an earphone , the site will recommend earphones from other brands .
But is this recommendation meaningful to a buyer ? Who on earth would you buy something similar to whatever they purchased recently especially if the product costs a lot ? People do buy similar products regularly, but it depends on the type of product you purchase.
For instance, if you buy a new book or blue ray disc of a popular movie , then it makes sense to recommend other book or movies from same author or genre. But when you buy a new blue ray player , what makes sense is to recommend blue ray disc and not blue ray players again.
So my ideal recommendation engine should be like :
If I buy a new DLSR , site should recommend to buy memory card or tripod or lens
If I buy an earphone and site has no related recommendation , then it should recommend only products that I have recently searched but not bought it yet. Or in worst case if there are no recommendation available , display latest offers instead of wasting the screen real estate
So what e-commerce sites needs to do is to have proper categorization of products and a suitable recommendation mapping so that it makes sense for the buyer to consider .